JPH01201484A - Chemical nickel plating liquid and method of using said liquid - Google Patents

Abstract

PURPOSE:To obtain a stable chemical plating liquid which can form a specific excellent plating film by dissolving hypophosphorous acid or the salt thereof as a reducing agent into an aq. nickel salt soln. and further combining and selecting complexing agents and adding the same thereto to prevent precipitation. CONSTITUTION:The hypophosphorous acid or the salt thereof is dissolved at 0.10-0.45mol./l as the reducing agent into the aq. nickel salt soln. contg. 0.09-0.20mol./l Ni and the complexing agents are so combined and selected as to prevent generation of the precipitation of nickel hypophosphite and nickel hydroxide equilibriously in the entire regions of the pH at the time of plating and the pH of an alkaline replenishing liquid, then said complexing agents are added to the soln. The complexing agents consist of 0.18-0.75mol./l malic acid, 0.14-0.50mol./l glycine, 0.09-0.30mol./l gluconic acid or ammonium and the pH of the aq. soln. is preferably adjusted to 4.0-7.0. The anionic surfactant of 1-200mg/l is preferably added further to this aq. soln. to obtain the stable chemical plating liquid. A nonmagnetic substrate consisting of an Al alloy, etc. is immersed in this plating liquid, by which the plating film having excellent heat resistant nonmagnetic characteristics is obtd. at a high plating speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a chemical nickel plating method and a chemical nickel plating solution used therein. The present invention relates to a chemical nickel plating method suitable for substrate processing of, for example, magnetic disks, particularly sputtered magnetic disks, and a chemical nickel plating solution used therein.

[Conventional technology]

The history of chemical nickel plating technology is long, and various techniques are known. The liquid composition aimed at stabilization, and the metal surface technology [Kin Hyoji 34]
．． 330 (1983)) Nioite systematically investigated thermal changes in the concentration of phosphorus and magnetic properties in chemically plated films, and found that trisodium citrate was used as a condition for obtaining a stable nonmagnetic layer base. Examples have been reported in which a cationic surfactant, that is, a cationic surfactant, is used in the complexing agent liquid.

[Problem to be solved by the invention]

The plating solutions of the prior art described above have many disadvantages in terms of stability of the plating solution and properties (mainly magnetic properties) of the resulting plating film. For example, a chemical nickel plating process that uses hypophosphite as a reducing agent can form a nickel plating film containing phosphorus, but since this nickel plating film exhibits non-magnetic magnetic properties, It is attracting attention as a base film. This type of phosphorus-containing nickel plating film has been used as a base film for a recording magnetic metal thin film formed by sputtering on a disk substrate such as an aluminum alloy.

However, due to the composition of the plating solution, the solution is unstable, nickel precipitates in the plating tank during use, and the solution must be replaced frequently, and the resulting plating film should be non-magnetic. However, there was a problem in that it had magnetism and could not function satisfactorily as an underlayer.

The purpose of the present invention is to solve these conventional problems, and the first purpose is to provide a plating solution for chemical nickel plating that can obtain a phosphorus-containing nickel plating film with excellent heat-resistant and non-magnetic properties. The second objective is to provide a stable chemical nickel plating method suitable for achieving the first objective.

[Means to solve the problem]

Next, the first object is achieved by a plating solution having the following composition. In other words, the first aspect of the present invention is to dissolve hypophosphorous acid or its salt as a reducing agent in a nickel salt aqueous solution, and to dissolve either hydroxy acid, glycine, and gluconic acid or ammonium as a complexing agent. The plating solution is characterized by:

Further, the features of the present invention are listed below.

(1) The hydroxy acid is one selected from malic acid, citric acid, glycolic acid, and tartaric acid.

(2) The chemical nickel plating solution is prepared by adding hypophosphorous acid or its salt as a reducing agent to a nickel salt aqueous solution, and dissolving malic acid, glycine, and gluconic acid as complexing agents.

(3) The concentration of nickel constituting the chemical nickel plating solution is 0.09 to 0.20 mon/Q, the concentration of hypophosphorous acid is 0.10 to 0.45 vao Q/Q, and the concentration of malic acid is 0.18. -0.75mo Q/Q, glycine concentration is 0.14-0.50mo Q/Q, and gluconic acid concentration is 0.09-0.30rao Q/Q.

(4) The chemical nickel plating solution is prepared by adding hypophosphorous acid or its salt as a reducing agent to a nickel salt aqueous solution, and dissolving malic acid, glycine, and ammonium as complexing agents.

(5) The chemical nickel plating solution has a nickel concentration of 0.09 to 0.20 mon/Q, a hypophosphorous acid concentration of 0.10 to 0.45 mon/Q, and a malic acid concentration of 0. 18 to 0.15 mon/12, glycine concentration of 0.14 to 0.50 mo Q/Q, and ammonium concentration of 0.09 to 0.30 mo Q/Q.

(6) An anionic surfactant is added to the chemical nickel plating solution.

(7) The anionic surfactant is selected from the group consisting of polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene alkyl ether phosphate, alkyl phosphate, and alkyl sulfate. or at least one selected from the group consisting of fluoroalkyl carboxylic acid, fluoroalkyl sulfuric acid, fluoroalkyl phosphoric acid, and salts thereof.

(8) The concentration of the anionic surfactant is preferably 1M
Must be between 72 and 200 mg/l.

(9) More preferably, the concentration of the anionic surfactant is 5 mg/A to 100 mg/l.

(lO) The pH of the chemical nickel plating solution is preferably 4.0 to 7.0.

The second objective is achieved by a plating method having the following configuration. In other words, the second aspect of the present invention is a step of preparing a desired substrate to be plated; a step of activating the surface of the substrate to be plated; and adding hypophosphorous acid to the activated substrate to be plated in a nickel salt aqueous solution. or by immersing it in a chemical nickel plating solution prepared by adding a salt thereof as a reducing agent and dissolving either hydroxy acid, glycine, and either gluconic acid or ammonium as a nickel ion complexing agent. The method is characterized by comprising a step of performing chemical nickel plating; and a step of lifting the substrate from the chemical nickel plating solution, cleaning it, and drying it.

Furthermore, the features of the present invention are listed below.

(1) The hydroxy acid is one selected from malic acid, citric acid, glycolic acid, and tartaric acid.

(2) The substrate to be plated is made of a non-magnetic substrate.

(3) As the activation treatment, a metal film having a higher ionization tendency than nickel is formed on the substrate to be plated.

(4) Adding an anionic surfactant to the nickel plating solution.

(5) The nonmagnetic substrate is made of one of aluminum alloy, magnesium alloy, ceramics, glass, and plastics.

(6) Forming a zinc coating as a metal coating that has a greater ionization tendency than the nickel.

In the present invention, as mentioned above, the substrate to be plated is not necessarily limited to non-magnetic substrates, but the effect is particularly great when applied to magnetic disks. The characteristics will be explained in detail.

Although phosphorus-containing nickel plating film (hereinafter referred to as N1-P chemical plating film) is essentially excellent as a base film for magnetic disk substrates, it has problems in practical application for the reasons mentioned above. Here, the characteristics necessary for the base film of a substrate for a sputtered magnetic disk (meaning a thin magnetic metal film for recording formed on a disk substrate by a sputtering method) will be described in more detail below.

(1) The base film must maintain nonmagnetic properties even during high temperature heat treatment required when forming high temperature heat resistant nonmagnetic recording media and protective films by processes such as sputtering. Practically speaking, it is necessary to maintain non-magnetism with a magnetic flux density of 5 G or less even after heating at 250° C. for about 3 hours.

The amorphous N1-P chemically plated film has the essential property of crystallizing and changing into a ferromagnetic material by high-temperature heat treatment.

The heat-resistant nonmagnetic property of the N1-P plating film depends on the phosphorus content in the film,
It is strongly related to the amorphous structure itself as well as the concentration of impurity elements such as Fe and Go. Regarding the film composition, it is of course necessary to use a plating solution composition that achieves a high phosphorus content and to use chemicals with a low content of impurity elements such as iron.

Regarding the film structure, EXAFS analysis, which is well-known and effective for structural analysis of amorphous materials, was performed and investigated. As a result, it was found that even if the film composition has the same phosphorus content, films with different film structures may be formed depending on how they are made, resulting in differences in heat-resistant nonmagnetic properties.

Therefore, when determining and selecting the liquid composition of a heat-resistant non-magnetic nickel plating solution for sputtered magnetic disks, it is necessary to consider the structure of the resulting plating film.

Figure 1 shows the experimental results obtained by EXAFS structural analysis. The figure focuses on the ratio (vertical axis) of the coordination number of N1-P to the coordination number of Ni-Ni in the film, which is determined by EXAFS analysis (details omitted). A high ratio means that there is a high probability that Ni in the film is coordinately bonded to P, and chemically, it means that the film has excellent heat-resistant nonmagnetic properties.

The horizontal axis in the figure is the ratio of the number of P atoms/the number of Ni atoms, which is a measure of the composition. The coordination number ratio of the plating film created using the plating solution of the present invention (shown by the solid line) tends to be higher than that ratio of the conventionally known plating solution (shown by the broken line), and even films with the same composition have essential structural differences. It can be seen that the material has better heat resistance and non-magnetic properties.

The reason why the coordination number ratio shown in the figure improves when the plating solution of the present invention is used is not clear at present, but it is speculated that the reaction during the growth process of the plating film It seems that the adsorption state of nickel and complexing agent on the surface is closely related to the structure of these films.

Regarding the phosphorus content, if it is less than about 11 wt %, magnetization tends to occur after heating, which is undesirable, resulting in the formation of a phosphorus content. P Necessary for plating film.

(2) Defect-free substrate Since defects in the plating film cause magnetic disk signal errors, strict defect-free properties that are not found in conventional plating films are required. Specifically, since the bit cell (minimum signal unit) of the current thin-film magnetic disk is about 1.0 μm×15 μl, a defect with a diameter of about 2 to 3 μm or more in the plating film will cause a signal error.

Therefore, if we take a disk with a diameter of 5 inches as an example, it will be 25 mm on both sides.
In principle, there should not be a single defect of the above size in the area of 0-.

In order to achieve a defect-free plating film, it is necessary to select AQ materials, keep the working environment clean, and perform high-precision filtration of the plating solution, but also to improve the stability of the plating solution itself. It is particularly important to eliminate the generation of foreign matter and decomposition products from the plating solution, and the stability of the plating solution is also required in this respect.

In this respect, the plating solution of the present invention is excellent as will be described later.

(3) Internal Stress A high level of flatness and smoothness is required to achieve head flying properties on the magnetic disk surface. - To give an example, the surface roughness is about 0.001 μm Ra, and the flatness (disc warpage) is 1 for a diameter of 210 mm.
It is strict, being less than 0 μm.

If the N1-P plating film on the substrate surface has high internal stress (also called plating film residual stress) and thick plating occurs on both sides of the board after processing, this will cause the board to warp and become flat. The flying ability of the head deteriorates due to
Not used as a magnetic disk substrate.

When a plating film is heat-treated, this internal stress is generated.

According to the above EXAFS structural analysis, it was found that a structural change occurs when an amorphous substance crystallizes, and this is the cause of internal stress generation.

Practically speaking, the internal stress after heating at 250°C for 3 hours is 2.
0 kg/m" or less. In order to reduce this internal stress, the selection of additives in the plating solution composition is particularly important. On this point, in the present invention, as will be described later, It was found that ionic surfactants act effectively.

Its film properties include hardness, corrosion resistance, surface roughness after plating, adhesion to the AI2 substrate, and uniformity of plating thickness distribution.

On the other hand, the characteristics of N1-P plating solution for magnetic disks include: (1) Plating solution life (stability, practically 4
．． Approximately 0 tan is required. Here, one turn means that the nickel at the time of bath preparation is replenished.

(2) Plating speed (Practically speaking, 7 μm)
/hr) and (3) ease of solution management are particularly important, and an N1-P plating solution that simultaneously achieves the above-mentioned plating film properties and these plating solution properties is required. According to the research conducted by the present inventors, there is no conventional plating solution that can achieve the above-mentioned characteristics, and this has been made possible for the first time by the present invention.

Conventionally well-known examples are shown in Table 1 for reference, but sample Nα
In example 1, the heat-resistant non-magnetic properties are almost good, but the internal stress value is 4.5 kg/+m" or less than the required value of 20 kg/+m".
5kg/m”, which is about twice as large.

Another problem is that the life of the plating solution is as short as 2.5 turns, and, probably related to this, there are many surface defects. The plating rate is also low compared to the practical level of 7 μIIl/hr. In the example of 'Nα2, the plating rate is Xo, 0 μm/hr, which is a sufficiently practical value, but there are problems with internal stress and heat-resistant non-magnetic properties, and the frequency of defects is high.

As a result, it is unsuitable as a base N1-P film for sputtered magnetic disks.

In the example of Nα3 in the table, there are no problems in plating speed and heat-resistant nonmagnetic properties, but there is a risk that the substrate is likely to warp due to large internal stress, and the stability of the plating solution and defects are also insufficient. Therefore, this plating solution cannot be applied to N1-P plating for disk substrates at a mass production level.

In other words, among the conventionally well-known plating solutions, there was no plating solution that could achieve all the severe characteristics required for sputter disk substrates. As mentioned above, the present invention makes this possible.

In other words, in the present invention, the stability (life) of the plating solution
The obtained film satisfies film properties such as high heat resistance, non-magnetism, low defects, and low internal stress while ensuring the following.

[Effect]

Several reaction mechanisms have been proposed for chemical nickel plating, and according to one of them, nickel ions, the main component, and hypophosphorous acid (H2pox-), the reducing agent, react during a nascent stage on the catalyst surface. Based on the intervening group of atomic hydrogen (He),
It is thought that the process proceeds through an autocatalytic chemical reaction. An example of an elementary reaction currently proposed is as follows.

That is, nickel ions are reduced to form a nickel metal film according to formula (3), while hypophosphite radicals are reduced according to formula (2),
As shown in (5), it is oxidized to become phosphorous acid, and a part of it precipitates phosphorus (P) as shown in formula (4) and is contained in the plating film.

Therefore, the constituent components of chemical nickel plating solution are nickel salt, which is the main raw material, hypophosphorous acid, which is the reducing agent,
It consists of a complexing agent to stabilize the plating solution and achieve good film quality, and additives to improve film properties.

The effects of each component in the plating solution will be explained below. First, the most important component, the complexing agent, will be described below.

(1) Regarding the complexing agent: The complexing agent in the chemical nickel plating solution is the most important factor governing the stability of the plating solution and the quality of the plating film. In order to develop a high-performance plating solution, the present inventors analyzed the action mechanism of complexing agents, determined the optimal complexing agent and its concentration, and found that hydroxy acids, glycine, and gluconic acid It has been found that a three-component combination of either ammonium or ammonium is effective. Therefore, the background that led to the invention of these complexing agents and the effects of the complexing agents will be described.

Looking at the reaction equations (2) and (5) presented earlier, as the plating reaction progresses, phosphorous acid (HxP) is added to the plating solution.
03-) accumulates. This phosphorous acid reacts with nickel ions in the liquid to produce hardly soluble nickel phosphite salt, which precipitates. These fine particles of nickel phosphite serve as the core of the plating reaction, so if the plating solution is used as it is, Ni powder will rapidly form in the solution and self-decompose. Even if it does not decompose, the plating film will be extremely rough and have many defects.

Therefore, a complexing agent is added to the plating solution to prevent this type of decomposition through its action, which will be described in detail later.

On the other hand, due to the main reaction of nickel precipitation in formula (3), a large amount of hydrogen ions (H) are generated in the solution, and the pH of the plating solution is
decreases rapidly and shifts to the acidic side. In order to maintain the pH of the plating solution constant, neutralization by adding alkali (usually adding caustic soda NaOH) is essential. This addition of alkali also causes the decomposition of the plating solution. In other words, when the pH of the aqueous solution of nickel salt alone is increased, from around p16 to nickel hydroxide (Ni(O
H)-1 is precipitated. In other words, when caustic soda is replenished to neutralize the plating solution, nickel ions that come into contact with the solution immediately precipitate nickel hydroxide (Ni(OH)).This is due to the plating reaction in the solution. They become nuclei and cause decomposition of the plating solution, or result in a plating film with many rough defects.Therefore, a complexing agent is added to the plating solution, and its action prevents this type of decomposition of the plating solution.As mentioned above. As shown above, the primary purpose of adding a complexing agent is to prevent precipitation and precipitation of nickel phosphite and nickel hydroxide, stabilize the plating solution, and reduce defects in the plating film.

This is because the complexing agent has the property of forming a complex bond with nickel ions and suppressing the concentration of nickel-free ions in the plating solution. Figure 2 shows the relationship between the concentration of nickel free ions (nickel ions not bound to the complexing agent) and pH for various complexing agents.

The results are shown based on conventional literature values and experimental values obtained by the present inventors. The diagonally shaded area A in the upper right corner of the figure is the region where nickel hydroxide is produced, and the shaded region B in the upper left corner is the region where nickel phosphite is produced. In other words, the diagonally lower left side (region C) in the figure is an area where no precipitation occurs. In an actual chemical nickel plating solution, it is usually necessary to contain about 0.1 mo Q/R as a nickel salt, and the pH is around 4.0 to 7.0. In order to prevent precipitation and precipitation of nickel phosphite in this pH range, the free ion concentration of nickel needs to be about 10-3+wo Q/Q or less, as seen from the figure.

From this point of view, by adding the complexing agent in equimolar amounts to the nickel salt, as can be seen from the figure, free nickel ions (N i+ + ) can be reduced by several orders of magnitude.

In this way, free nickel ions (N i+ *) are effectively reduced in the pH range of 4 to 7 in the plating solution used in actual use.

It has the effect of preventing the precipitation of nickel phosphite, but the order of magnitude of the effect of reducing free nickel ions is citric acid, malic acid, malonic acid, and succinic acid.

Next, we will discuss the concept when the pH is 7 or higher.

Considering the temporarily high pH (for example, 14) during alkali replenishment, the stability of the plating solution must of course be designed taking into account the pH range from 4 to 7 to 14 when the plating solution is used. Although this is clear, conventionally known plating solutions are insufficient in this respect. Precipitation area of nickel hydroxide (A
A complexing agent having characteristics in the lower left direction (region C) in the same figure is effective in order to move as far away as possible from the region (region C). From the same figure, when comparing the magnitude of the free nickel ion reduction effect in the region p) 17 to 13, glycine>glutamic acid>
citric acid>. Furthermore, as shown in the figure, gluconic acid and ammonium were found to be effective complexing agents even at highly alkaline conditions of pH > 13, and this was also confirmed experimentally. This point was lacking in conventional plating solutions, and by focusing on this point, the present invention was able to significantly improve the stability of the plating solution.

That is, in the entire pH range from the pH when the plating solution is actually used to the high pH of the alkaline replenishment solution (around pH 14), the complexing agent is The key point of the present invention is to configure the following in combination.

By stabilizing the plating solution based on the above-mentioned principle, it is possible to prevent the generation of fine particles due to decomposition of the plating solution itself, and it is possible to significantly reduce the occurrence of defects in the plating solution obtained due to this type of cause.

Next, the relationship between the concentration of the complexing agent added and the free nickel ion (N x + 4 ) concentration will be described using FIG.

The horizontal axis of the figure represents the complexing agent/Ni salt molar ratio.

The vertical axis is the free nickel ion concentration in the plating solution (
In other words, it shows a nickel ion that reacts with a complexing agent and does not harm the enemy. As can be seen from the figure, free nickel ions are rapidly reduced by the addition of each complexing agent. The tendency is that the decreasing effect is remarkable up to a molar ratio of about 2, after which it follows a gradual decreasing trend and approaches equilibrium at a molar ratio of about 5 to 6. From these data, in order to reduce free nickel ions and stabilize the liquid, it is preferable to add at least an equimolar amount of complexing agent to that of the Ni salt, and even if it is added in an excessively large amount, it is not necessary considering the high cost. has little effect.

In order to select a complexing agent, in addition to stabilizing the plating solution by focusing on the free nickel ions mentioned earlier, it is also necessary to consider film characteristics related to film formation, such as plating speed and heat-resistant nonmagnetic properties. . In particular, it is necessary to understand the film properties through experiments. Next, we actually created a plating solution using each complexing agent, determined the stability of the plating solution (number of turns), the plating speed (μm/hr), the heat-resistant non-magnetic property of the film (heated magnetization at 250°C), etc. amount, unit is expressed in Gauss G) 4 film surface defects (number of defects on the film surface, expressed in ke/surface) and internal stress (
kg/mm”).For this experiment, 300Q
Samples were prepared and evaluated using an experimental plating tank with a capacity of .

In the table, Samples 4 to 12 showed the characteristics of candidate materials for the main complexing agent that most influenced the plating film characteristics and plating solution characteristics. At this time, glycine and gluconic acid were used as sub-complexing agents that have a stabilizing effect on the alkali side.

Looking at the properties of the main complexing agent candidate, malic acid has excellent plating film properties and liquid properties. When the concentration of citric acid was increased, the plating rate tended to decrease drastically. Although the plating rate of glycolic acid and tartaric acid is somewhat low, other properties are relatively good. The above four types of complexing agents are hydroxy acid type, but the characteristics of malonic acid (NQII) and succinic acid (Na12) as dicarboxylic acid type complexing agents were investigated separately.

Malonic acid has problems in terms of liquid stability and heat resistance and non-magnetism, and the same is true for succinic acid.

From the above results, it was found that malic acid, glycolic acid, and tartaric acid are relatively good as main complexing agents, and malic acid is the most suitable complexing agent. We believe that citric acid can be used in a limited manner with the condition that a small amount of complexing agent is added. Malonic acid and succinic acid cannot be used as plating solutions for magnetic disks.

In relation to the complexing agent of the plating solution and the properties of the plating film, the findings obtained in this experiment show that hydroxyl complexing agents, which share a hydroxyl group (-OH) and a carboxyl group (-COOH) in their molecules, The objective is to have excellent properties that allow both high plating strength and heat-resistant non-magnetic properties.

The reason for this is not clear, but it is assumed that the geometry of the complex and the properties of the functional group affect the adsorption form on the reaction surface and the reaction rate, resulting in a relatively high plating rate. It is also easy to obtain film quality with a high phosphorus content, and therefore it is believed that it has high heat-resistant non-magnetic properties.

Among the hydroxy complexing agents, chain compounds had excellent properties, while aromatic complexes had poor properties.

In addition, the properties of the plating film formed from a dicarboxylic acid complexing agent such as Nα11.12 in Table 2 shown in the comparative example were not good.

Sample numbers 13 to 17 in Table 2 exhibited characteristics of candidate sub-complexing agents that act mainly in the alkaline region and contribute to stabilization of the plating solution.

For N1113.14, the characteristics of the glycine-ammonium combination sub-complexing agent were investigated, and the film quality and liquid properties were both good. It was found that the film properties were equivalent to or better than those of the above.

In the samples of Nα13.15.16.17, malic acid, which has the best properties, was used as the main complexing agent, and ammonium was used as the sub-complexing agent, which contributes to stabilization on the high alkaline side. The results of investigating the properties of candidate sub-complexing agents that contribute to this are presented.

As a result, glutamic acid of Nα15 has many plating defects,
The stability of the liquid was somewhat insufficient. Citric acid with Nα16 has a low plating rate. In the case of Nα17, it was not used due to insufficient stability.

As a result, it was found that the plating solution composition using glycine of Nα13 as one of the sub-complexing agents was the most excellent.

To summarize the above results, malic acid is the most excellent complexing agent for plating solutions, followed by glycolic acid,
Tartaric acid is the most likely, and citric acid can also be used within a limited range.

As the sub-complexing agent, a combination of glycine-gluconic acid or a combination of glycine-ammonium is suitable.

In other words, the combination of malic acid-glycine-gluconic acid,
It is found that the combination of malic acid-glycine-ammonium has the best plating solution properties and film properties.

Na 18 to Na 22 in the table are the results of an experiment conducted to confirm that if even one is omitted from this combination, the stability of the plating solution cannot be maintained.

All of the plating solutions with Nα of 18 to 22 decomposed before the practical life of the solution (4.0 turns). In other words, the basis of the present invention is to use the three components of malic acid, glycine, and gluconic acid, or the three components of malic acid, glycine, and ammonium as complexing agents, and this makes it possible to
In steps 1 to 14, the stability of the liquid can be ensured and the membrane properties of the resulting membrane can be significantly improved.

In addition, FIG. 4 shows the interaction between the complexing agents malic acid, glycine, gluconic acid, and ammonium in the present invention in more detail in relation to the comparative example Nα12.13°14 in Table 2 above. .

The figure also shows how synergistic effects are exerted by the interaction of each component. The figure shows the practical and preferable addition range of each complexing agent.

(2) Regarding nickel salt; Next, nickel salt, which is the nickel component of the plating solution, will be described.

As is well known, nickel salt is the main raw material for the intended nickel plating film. Any water-soluble nickel salt may be used, and sulfates, chlorides, sulfamates, acetates, etc. are common.

Especially considering economic efficiency, sulfate (nickel sulfate) is practical. The concentration of nickel is 0.09 to 0.20m, as detailed in Tables 4 and 5.
On/n is preferred. 0.09mo 42/
If it is less than Q, it will be difficult to obtain a practically required plating rate of 7 μm/hr or more, and if it is more than 0.20 mon / 2, the plating solution will become unstable, defects will easily occur, and the quality of the obtained film will deteriorate.

(3) Regarding hypophosphorous acid as a reducing agent: As mentioned above, primary hypophosphorous acid or its salt is a reducing agent in the plating reaction, reducing nickel ions (Ni'') in the plating solution to metallic nickel. Sodium salt is usually used because it is economically easy to obtain.However,
It goes without saying that pond water-soluble salts such as potassium salts can also be used.The concentration of hypophosphite suitable for use is 0.10 to 0.4, which will be explained in detail later.
5mo A/(1 is preferable. If it is too low, the plating speed will decrease, and if it is too high, the plating solution will become unstable.

(4) Regarding surfactants as additives: Next, we will discuss the effects of surfactants and preferred material selection. Surfactants adsorb to the surface of a plating film when it is formed, thereby affecting the properties of the film.In the present invention, by using an anionic surfactant, the internal stress of the plating film is significantly reduced. It is something.

When added in small amounts, surfactants have a remarkable effect on reducing internal stress. It has an effect. Therefore, the selection of surfactant is particularly important, and materials were selected by evaluating the internal stress of the plating film, liquid stability, plating speed, surface gloss, etc. The results are shown in Table 3.

Each sample was prepared in the same manner as in Table 2 above, and the samples containing Na and Na without any additives had too large an internal stress to be practical. A cationic surfactant of Na type has the problem of making the plating solution unstable and has little effect on reducing the internal stress of the film. Although a trialkylbenzylammonium salt was shown as a representative example of a cationic type, other cationic types also had poor characteristics, although there were differences in degree. Nα whistle represents a nonionic surfactant,
Although the example of polyoxyethylene dodecyl ether was shown,
It is not suitable as an additive for the plating method of the present invention because it does not have an effect of reducing the internal stress of the film. Since the charge state of the surfactant in the plating solution has a strong correlation with the adsorption phenomenon on the plating growth surface, it is thought that the effect differs depending on the type of surfactant. to αn~g5
Here we will list materials that have excellent properties as anionic surfactants.

i) Sample Nα=, related to NaJh: polyoxyethylene alkyl ether sulfate chemical structural formula RO(
CH2CH20) n803M However, R: alkyl group (
lipophilic group) M: Na + K + N H4 or HN (C,
H, OH).

n: 0 to 10 Specific examples: *Sodium polyoxyethylene dodecyl ether sulfate, *Polyoxyethylene octyl ethyl sulfate 2) Related to sample Na: Polyoxyethylene alkyl ether phosphate■ Chemical structure (RO(CHz CH20)n)m P
(OM) QHowever, R, M: Same as above n: 0 to 10 m=1. Q=2 or m=2. Q=1 Specific example: *Polyoxyethylene octadecyl ether ammonium phosphate zs bowl ni) Sample Nn441-, Na related to: polyoxyethylene alkyl phenyl ether sulfate However, R, M: Same as above n: 0 to 10 Specific example: x Sodium polyoxyethylene nonylphenyl ether sulfate x Sodium polyoxyethylene hexadecyl phenyl ether sulfate Chemical structural formula CnFmH (2n+t-m) -〇〇〇M
However, n: 6-20 m: 13-41 M: H, Na, K or NH4 Specific example: x Potassium pentadecafluorocaprylate x Tetracosafluorostearin fluoroalkyl sulfate Chemical structural formula CnF+++H (2n+1-m)- 080
3M However, n: 6-20 m: 13-41 M: H, Na, K or NH4 Specific examples: * Sodium tridecafluorohexyl sulfate * Ammonium tricosafluorononadecyl sulfate 2 g vi) Sample related to Na erection: Fluoroalkyl phosphate chemical structural formula CnFmH(2n++-m)-0-P-O
MOH However, n: 6-20 m: 13-41 M: H, Na, K or NH.

Specific example: x potassium hebutadecafluorooctyl phosphate x ammonium eicosafluorodecyl phosphate x tricosafluorooctadecyl ■ Chemical structural formula (RO)n-P-(OM)m However, R:
Alkyl group (lipophilic group) M: Na, K or NH.

Specific example: *Peroxyethylene lauryl realyl sulfate salt Chemical structural formula RO8O,M Where, R: Alkyl group (lipophilic group) M: Na, K or NH4 Specific example: *Alkyl of lauryl sulfate sodium surfactant The group may be a linear compound or a compound with a side chain, and is not particularly limited.

The amount of anionic surfactant added to the plating solution in the present invention is preferably 1.0 mg/l to 200 mg/12, more preferably 5 mg/l to 100 mg/l.

If it is less than 1.0 mg/l, the effect will be small; on the contrary, if it is less than 200
Addition of more than mg/l does not increase the effect of surfactant addition; in fact, too much addition causes adverse effects such as the tendency for defects to occur in the film.

The present invention will be explained in more detail below with reference to Examples.

〔Example〕

Example 1 An example will be shown in which a magnetic disk substrate was actually formed using a plating solution according to the present invention and its characteristics were evaluated. The substrate forming steps are shown below in order of process.

After forming a Zn film for metallization on the AQ-Mg alloy of the magnetic disk substrate that will be the substrate to be plated,
This is the order of forming the 1-P plating film.

(1) AQ board φ210-φ40 A
Ω-Mg material (2) Alkaline cleaning commercially available solution
Immersion at 50℃ for 15 minutes (3) Acid etching
Commercial solution 60℃ 3 minutes (4) HNO, washing
30wt%HN0. 23℃ 1 minute (5) Zinc replacement Commercial solution 23℃ 1 minute (6)
HNO, washing Same as above 23℃ 1 minute (7) Zinc replacement Same as above 23℃
0.5 minutes (8) Chemical N1-P plating Inventive plating solution 90°C approximately 120 minutes (9) Hot water washing
Pure water, 90° C., 5 minutes (10) Dry After polishing, proceed to the medium forming step Note that washing with pure water is performed between each of the steps (2) to (9) above, but the description is omitted.

The main points of the above formation process are that the substrate is made of AQ material, and the concentration of additives and impurities of the AQ material.

Consideration must be given to crystal grain size, crystallized substances, and inclusions.

The zinc substitution treatment was carried out twice, as is commonly done, in order to improve adhesion. Washing with pure water between processes is particularly important, and it goes without saying that careful attention should be paid to the purity of the water used and the washing method.

The results will be detailed in Table 4 below, but before doing so, the method for measuring and evaluating the characteristics of the nickel plating film shown in this example will be described in advance.

(1) Amount of heating magnetization 8X8° by N1-P plated sample on AI2 substrate
A sample is cut out and heat treated. The heat treatment was carried out using an ordinary electric furnace at a heat treatment temperature of 250±2.5° C. and a holding time of 3 hours. Atmosphere is air.

After the heat treatment, the BH hysteresis curve of the sample was measured using a vibrating sample magnetometer (VSM) at a maximum excitation magnetic field of 10 KOe. The amount of heating magnetization listed in Table 4 is the amount of magnetization with an applied magnetic field of 10 KOe. Base run is 8x80
The AQ substrate itself was used.

(2) Form a N1-P plating film on the internal stress AQ substrate, and
A rectangular sample is cut out from the disk substrate that has been heat-treated for several hours, and only the N1-P plating film on one side of the sample is removed by etching using nitric acid. If internal stress exists in the N1-P plating film, this will deform the sample and cause warping. Measured warpage amount of sample before and after etching, plating thickness, AQ
The internal stress was calculated from Young's modulus and AQ thickness.

(3) Surface defects N1-P Polishing was performed after plating, and defects on the mirror-finished disk substrate surface with a surface roughness of about 0.001 μm Ra were observed and measured. The measuring device irradiates the sample surface with laser light obliquely and detects surface defects based on the scattered light.

The resolution is variable and can be detected from a minimum of 1.0 μm, but
In the case of this example, the detection limit was measured as a defect with a diameter of 3 μm or more. For the sample, 50 5-inch diameter substrates were prepared.
Both sides were measured, and the number of defects in a total of 100 sides was counted. In most cases, there was only one defect on one surface, and there were very few cases where there were two or more defects. Therefore, if the data in the table is n/100 surfaces, it is almost agreed that out of 100 surfaces observed, there was one defect on each n surface.

(4) Plating rate The weight of the disk substrate before and after plating was measured using a chemical balance, and the plating rate was calculated from the surface area, specific gravity, and plating time. When measuring the film thickness distribution, a fluorescent X-ray film thickness meter was used.

(5) Stability of plating solution While plating was performed in a 300Q plating bath, stability was determined from the film characteristics of the plating film and the plating solution properties such as plating speed, deposition potential, solution component concentration, and condition.

The life of a plating solution is expressed in terms of the number of turns, and one turn is the amount of plating solution used until the Ni at the time of bath preparation is completely replaced by subsequent replenishment.

As the plating solution is used, sodium phosphite and sodium sulfate accumulate as waste products in the plating solution. Therefore, although the saturation solubility of these salts is the theoretical limit of the life of a plating solution, in reality, the life is determined by an increase in defects before this point. Practically speaking, a liquid life of about 4 tans is required.

(6) Phosphorus content in plated film After dissolving a certain amount of the film in nitric acid, the phosphorus content was analyzed using an ICP plasma emission spectrometer.

N1-P plating of a 5-inch diameter disk substrate was performed using industrial chemicals in a 300Q experimental tank.

In this example, the above-mentioned compatible concentration range of the complexing agent, compatible concentration range of nickel and reducing agent, and compatible range of pH value with these were determined experimentally and clarified.

That is, a solution containing a combination of malic acid, glycine, and sodium gluconate and a solution containing a combination of malic acid, glycine, and ammonium were used as complexing agents, and their concentrations were varied.

When changing the concentration, take into account the complexing agent and nickel-free ion concentration results shown in Figure 2 above, and make sure that malic acid is at least twice the molar concentration of nickel, and glycine is at least 1.0 times the molar concentration of nickel.
Care was taken to keep the molar concentration at least 5 times that of nickel, for gluconic acid at least 1.0 times that of nickel, and for ammonium at least 1.0 times that of nickel.

Table 4 shows the results for the malic acid-glycine-gluconic acid combination solution, and Table 5 shows the results for the malic acid-glycine-ammonium combination solution.

The results of the experiments shown in Table 4 show that nickel sulfate's good speed decreases in the range of 0.09 to 0.20moQ/Q, and that if the Ni concentration is too high, it loses the heat-resistant nonmagnetic properties required for practical use. This resulted in the problem that it could not be maintained and the number of defects increased.

z Sodium hypophosphite is 0.10r as shown in Nam
If the concentration is less than soQ/Q, the plating rate will be low and it will not be practical.
If the concentration is 5mo Q/2 or more, the plating solution tends to become unstable, so the preferred concentration is 0.10 to 0.45mo.
It turned out to be Q/Q.

pH is a particularly important element in the plating solution composition, and as a macroscopic trend, lowering p)I tends to stabilize the plating solution, but has the disadvantage that the plating speed decreases.
Conversely, when the pH is increased, the reduction driving force of the reducing agent increases and the plating rate increases, but on the other hand, the plating solution becomes unstable and the possibility of precipitation and decomposition increases. As a result of the above, the plating characteristics deteriorate in this embodiment.

The additives used in this example include sodium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxide dodecyl ether sulfate, and heptadecafluorooctyl, which have relatively excellent properties according to the results shown in Table 3 above. Three types of potassium phosphate were used. The additives are not limited to these materials, and it goes without saying that good properties can be obtained using the anionic surfactants listed in Table 3 above.

A plating solution was prepared by varying the concentration of each component in the plating solution within the above-mentioned concentration range, and the characteristics of the plated film, plating speed, and solution stability were measured and summarized.

3') Since we believe that IP ≦ or less, we have achieved 20 kg/m2 or less for these samples from Nc to Nα villages. These Na'J
When the polished surfaces of the P - Ab NQ+4 samples were measured using a laser defect detection device, the number of defects (φ3 μm or more) ranged from 0 to a maximum of 5 per 100 surfaces. Observation of these defects using an optical microscope and a scanning electron microscope (SEM) revealed that these defects were caused by foreign matter, dust, etc. being incorporated into the plating film, or by defects in the AFL substrate. This defect was not thought to be related to the characteristics of the plating solution.

Generally known commercially available N1-P for disk substrates.
When compared with the fact that the defect occurrence rate in plating films is around 5% to 10%, the results of these examples of the present invention are considered to be comparable to those of the conventional technology, and it can be seen that the plating solution is sufficiently durable for practical use. .

P=11.0 to 13.0 wt% when the plating rate reached 7.0 μm/hr or more, which is a practical plating rate. The phosphorus content is one of the factors that determines the amount of heating magnetization.

The surface roughness after N1-P plating is about 0.04 μmRa.

The plating solution life can be confirmed to be 3.8 to 4.5 turns.
Almost achieved a practical 4.0 turn.

To summarize the results of this example summarized in Table 4,
Nickel concentration is 0.09~0.20+so Q/Q
, malic acid concentration is 0.18-0.75 mo Q /Ω,
Glycine concentration is 0.14-0.5vao Q/Q,
Gluconic acid concentration is 0.09-0.30mo Q/Q
, Sodium hypophosphite concentration is 0.10-0.45ya
o Q/Q, pH is in the range of 4.0 to 7.0
In view of the 1-P film characteristics and the plating solution characteristics, it can be seen that the composition range is suitable for obtaining a base N1-P plating film for a magnetic disk.

Example 2 Next, the results of the malic acid, glycine, and ammonium baths shown in Table 5 will be described.

As a result of the experiment, firstly, the good speed of nickel sulfate decreases in the range of 0.09-0.20moQ/Q, and if the Ni concentration is too high, it is impossible to maintain the heat-resistant nonmagnetic property required for practical use, resulting in defects. This caused the problem of an increase in the number of people.

9 Sodium hypophosphite is 0.10/as shown in Nα→
If the concentration is less than mo Q / Q, the plating rate will become low and it will be impractical. Conversely, as shown in Naf; 4, if the concentration is more than 0.45 mo Q / 0, the plating solution tends to become unstable, so it is preferable. The concentration is 0.10-0.4
It was found to be 5mo Q /Q.

p) I is a particularly important element in the plating solution composition;
As a macroscopic trend, lowering the pH tends to stabilize the plating solution, but the disadvantage is that the plating speed decreases.
Conversely, when the pH is increased, the reduction driving force of the reducing agent increases and the plating rate increases, but on the other hand, the plating solution becomes unstable and the possibility of precipitation and decomposition increases. As a result of the above, in this example, the plating characteristics deteriorate.

In this example, two types of additives, sodium polyoxyethylene lauryl ether sulfate and triethanolamine lauryl sulfate, were used as additives that had relatively excellent properties according to the results shown in Table 3 above. The additives are not limited to these materials, and it goes without saying that good properties can be obtained using the anionic surfactants listed in Table 3 above.

A plating solution was prepared by varying the concentration of each component in the plating solution within the above-mentioned concentration range, and the characteristics of the plating film, plating speed, and solution stability were measured and summarized.

~15kg/++n'', and has achieved a practical target value of 20kg/mm'' or less. These Nα
When the polished surfaces of the samples from D to NQ■ were measured using a laser defect detection device, the number of defects (φ3 μm or more) was from OK to a maximum of 3 per 100 surfaces. The results of observing these defects using an optical microscope and a scanning electron microscope (SEM) show that all defects are of the type where foreign matter, dust, etc. have been incorporated into the plating film, and are thought to be related to the characteristics of the plating solution. It was not a defect that could be detected.

N1-P for disk substrates, which is usually known from literature, etc.
When compared with the fact that the defect occurrence rate in plating films is around 5% to 10%, the results of these examples of the present invention are considered to be comparable to those of the conventional technology, and it can be seen that the plating solution is sufficiently durable for practical use. .

Female 3: The plating rate shows p)I dependence, but NQ8-+I
-Nαv≠ plating solution is 1.0prll/hr ~15. Own
+/hr, which is a practical plating speed of 7.0 μm.
/hr or more, P was 11.5 to 13.2 wt%. The phosphorus content is one of the factors that determines the amount of heating magnetization.

Surface roughness after N1-P plating is 0.04 μva Ra
That's about it.

The life of the plating solution was confirmed to be 4.5 to 5.0 turns, and the practical 4.0 turns was achieved with a margin.

To summarize the results of this example summarized in Table 5,
Nickel concentration is 0.09-0.20mo Q/Q,
Malic acid concentration is 0.18-0.75mo Q/Q,
Glycine concentration is 0.14-0.5mo Q/Q, ammonium sulfate concentration is 0.09-0.30mo Q/
Q. Sodium hypophosphite concentration is 0.10-0.45
vao Q/Q, pH is in the range of 4.0 to 7.0, which is a suitable composition range to obtain a base N1-P plating film for magnetic disks, in view of N1-P film characteristics and plating solution characteristics. I understand.

Although the composition of the complexing agent in Tables 4 and 5 is different, when comparing the characteristics of the two, the malic acid-glycine-ammonium bath in Table 5 tends to have a slightly longer lifespan of the plating solution. , exhibits characteristics with slightly fewer plating defects. This is thought to be due to the difference in complexing ability between ammonium and gluconic acid, but the detailed mechanism is currently unknown.

Although the plating solution of the present invention brings out the action of the complexing agent in the entire pH range and is essentially stable, the plating solution of the present invention contains Pb, which is known as a component of ordinary chemical nickel plating solutions.
, TQ'' decomposition inhibitor, boric acid, EDTA, and other stabilizing additives may of course be added.

In addition, in the above example, the temperature of the plating solution was set at 90°C, but it is practically effective in the range of 80 to 95°C, so the storage stability of the solution at room temperature is extremely stable. Easy to manage.

Embodiment 3 In this embodiment, 1, which actually produces magnetic disks,
The results of confirming the characteristics of the plating solution according to the present invention using a large plating tank of 50 (IQ) will be described below.

The contents of the basic N1-P plating process are the same as those described in Example 1. The plating equipment is a line with a pre-treatment tank and a plating tank arranged in the order of the process, and the entire equipment is Class 1,
It was installed in a 000 clean room. The rack jig for setting the disk substrates is a revolving type jig that can mount up to 600 disk substrates with a diameter of 5 inches. It is a mechanism that uses the inner circumference of the board to rack, and all mounting and removal of the board to the jig is automated.

The filter accuracy is 0.2μm, and the plating load ratio is 1. The load is Odn+”/Q.

Table 6 shows the results of experiments conducted in a 1,500Q production plating tank and evaluation of characteristics. From the experiments shown in Tables 4 and 5 above, we selected a plating solution composition in which the overall plating film properties and plating solution properties were particularly suitable.
Four types of cleansing liquid were used up to Mocha's first run, but an alkyl-based surfactant with a high concentration of nickel sulfate was used.

pH and sodium hypophosphite are particularly important factors that are closely related to the plating rate, and each pH is between 4.7 and 5.
0 range, Na hypophosphite is 0.28-0.30rn
o They were combined as shown in the table within the range of Q/Q. All industrial chemicals were used to prepare the plating solution.

To summarize the characteristics of the N1-P film produced under the above plating conditions, the amount of magnetization when heated at 250°C is 0.6 to 2.0G.

Internal stress after heating at 250℃ is 8-15kg/rrtn2
All of them are below the target value of 5G at the practical level, 20
kit/+nm” or less.

After polishing, there were 0 to 3 plating defects of φ3 μm or more out of 100 surfaces inspected. This can be expressed as wax,
3.0%, which is considered to be relatively excellent. The plating speed is 7.5 to 9 for the target of 7.0 μm/hr or more.
．． 0 μm/hr was actually measured. The life of the plating solution was confirmed by Nα, and it was confirmed that the plating solution was sufficiently durable for practical use.

Although both complexing agent compositions achieve the target properties, the malic acid-glycine-ammonia bath tends to be slightly better than the malic acid-glycine-gluconic acid bath in terms of plating solution life and plating defects. show.

An example in which a magnetic film and a protective film were formed using an N1-P plated substrate prepared using the plating solution shown in Table 6 above and evaluated as a magnetic disk will be described below.

The steps from the pretreatment of the AQ substrate to the formation of the N1-P plating film have been described previously, and will therefore be omitted.

The substrate after N1-P plating was then polished. This was done using a polishing machine that can polish both sides at the same time. The substrate is sandwiched between two polishing surface plates, upper and lower, and polished by applying pressure and rotating the surface plates while supplying polishing liquid. The average amount of processing is about 3 μm, and the surface roughness after polishing is 0.001 μm Ra.

After the polishing process, the N1-P substrate was then placed in a surface cleaning device to perform surface cleaning. Surface stains were removed by cleaning using a method mainly using organic solvents and pure water.

After the surface cleaning, the N1-P substrate was then set in a continuous sputtering device. This sputtering apparatus is capable of successively laminating three layers: a chromium intermediate film, a magnetic film, and a carbon film.

The sputtering process will be explained below. The pallet loaded with the magnetic disk substrate was placed in the load chamber of the sputtering device and evacuated. After evacuation to a degree of vacuum of 5×10 −' Torr or less, the substrate was heated at 200° C. to degas the substrate surface. After that, the pallet is transferred from the loading chamber to the sputtering chamber, where two chromium (Cr) interlayer films are first deposited.
, 000 thickness.

The Cr film is formed for the purpose of adjusting the N1-P surface and stabilizing the magnetic properties of the subsequent magnetic film.

The pallet loaded with the substrates on which the chromium film has been formed is then automatically transported to the sputtering chamber where the magnetic thin film is formed. The magnetic film is a Go-Ni-Cr sputtered film.

Operating pressure during Co-Ni-Cr sputtering is 20mT
orr: Ar atmosphere, film formation rate is 200 people/min, and film thickness is 500 people/minute.

The substrate on which the magnetic thin film has been formed is then transported to a carbon sputtering chamber in order to form a carbon protective film thereon. The carbon was sputtered using 99.9% pure Targera 1 ~, and the film thickness was 500%.

After the carbon film was formed, the substrate was taken out from the sputtering device, and finally, lubricating oil was applied to the carbon surface. The lubricating oil is formed together with the carbon film to improve head sliding resistance and prevent damage to the magnetic film.

The above example describes one example of manufacturing a thin film sputter magnetic disk, and it goes without saying that the materials and film thicknesses of the intermediate film, magnetic film, protective film, and lubricating oil are not limited to these. . The N1-P substrate may also be subjected to a grooving process called texturing process after the polishing process.

Next, the shape of the finished magnetic disk after forming the carbon film was measured. The straightness of the disk, which indicates warp, is 4 to 6 μm for a 5-inch disk with a diameter of 130 mm, which is at a level that causes no problem with the head flying height of 15 μm in actual use.

The fact that this warpage is small means that the N1-
This is because the internal stress of the P plating film is kept low to 15 kg/no2 or less.

The surface roughness on the carbon after the disc is completed is 0.002
p mRa, the value before film formation (0,001μ111)
There are few changes compared to . During sputtering film formation, N1-
Although the P substrate is heated to a maximum of about 250° C., the N1-P film formed according to the present invention does not undergo heating magnetization or deterioration of surface roughness at this temperature, indicating that it is stable.

Next, the results of evaluating the electromagnetic conversion characteristics showed that the resolution was 75%,
Override (overwriting characteristics) -30dB and linear recording density 32,0OOB PI (bit/1nch)
was achieved with plenty of time to spare. This is also because the plated film according to the present invention maintains its nonmagnetic property even when heated to about 250° C. which is applied during sputtering. The disk flying characteristics, expressed as the number of protrusions that collide with the magnetic head flying when the head-disk spacing is 0.15 μm, were measured. , n=10 planes), which was extremely excellent.

The error characteristics are linear recording density 32,0OOB PI, track density 1,200T PI (track/1
Under the measurement conditions of nch), it was 0 to 20 pieces/side (average 5 pieces/side, n=10 sides), which was at the same level as a conventional coated disk, and there was no problem in practical use. This good error characteristic is considered to be because the plating solution for forming the N1-P plating film of the present invention is stable and the resulting plating film is less likely to have defects.

Finally, the reliability measure CSS (Contac
When the head sliding strength of the disk was measured using the test strength, it was measured more than 30 times (n=10) in each case, and it was confirmed that the strength was at a practical level.

As mentioned above in the margin below, the N1-P plating film formed according to the present invention has excellent heat-resistant non-magnetic properties, low internal stress, and defect-free properties, all of which are required as an underlayer for sputtered magnetic disks. By manufacturing magnetic disks using
We were able to confirm that it was possible to achieve excellent electromagnetic conversion characteristics, head flying characteristics, error characteristics, and reliability as a magnetic disk.

The present invention makes it possible to improve the performance and put the magnetic disk into practical use, and has a great effect on the information storage industry and surface treatment industry.

Embodiment 4 An embodiment of the plating apparatus according to the present invention will be described below with reference to FIG. The plating tank 1 is a rectangular tank with a liquid volume of 600Q, and the total volume including piping etc. is 700Q. The plating tank is a SUS frame lined with a 5.0I thick fluororesin such as PTFE SakiCF, -CF2-h+ or pVD F-6cF, -cFs-)-h, etc. It is. Reference numeral 2 denotes a replenishment section, which has a simple structure in which a fluororesin tubular pipe is provided with three introduction flanges so that replenishment liquid can be added through a check valve, and the liquid feeding rate is 200Q/min. The amount of liquid sent by the pump should be determined in consideration of the total amount of plating solution, and ensuring that the total amount of plating solution is circulated at least 10 times per hour, preferably 15 times or more, is the best way to reduce defects. This is one of the key points for obtaining a plated film.

4 is a filtration filter, and the contents include a 5 μm precision depth filter first, followed by 1 μm and 0.2 μm filters arranged in series.

Note that the filter precision may be further improved if necessary.

5 is a heating section, which is a fiber type heat exchanger and uses steam at 120° C. as a heating source.

10 is a plating solution analysis section, which is composed of a pH meter and an absorption photometer. A spectrophotometer measures the nickel concentration. The plating solution is continuously sampled from the plating tank, and after cooling to room temperature, the pH and nickel concentration are analyzed, and then the plating solution is returned to the plating tank. It has the ability to perform analysis every 5 minutes at the shortest.

11 is a replenishment liquid tank and a replenishment liquid pump, and this pump is a diaphragm type metering pump, and the amount of liquid sent is variable.

Reference numeral 12 denotes a control unit, which calculates the consumption amount of the components in the plating solution by inputting the above analysis results, replenishes the amount corresponding to the consumption amount by operating the replenishment solution pump for the required time, and controls the plating solution. Performs automatic control to keep the contents constant.

Examples will be described in detail below based on the actual work order. The substrate is an A2 alloy for magnetic disks with an outer diameter of 130 φ and an inner diameter of 40 φ and a thickness of 1.905 t, the surface roughness is 0.05 μm Ra, and the material is 5086 material. Set 300 of these substrates on a plating revolving jig. Pretreatment for plating was carried out in the usual manner by alkaline degreasing, acid etching, nitric acid treatment, first zinc substitution treatment, nitric acid treatment, and second zinc substitution, with sufficient pure water washing in between.

Next, the substrate is placed in a chemical nickel plating tank 1. The conditions for chemical nickel plating are shown below.

Plating solution temperature 90℃±0.5 Plating solution pH4.8±0.05 Plating thickness 15μm Plating time: 2 hours The plating solution used has the following composition.

NiSO4・6H, 025g/Q NaH2PO, -N20 30g/Q
Malic Ac1d (malic acid)
60g/QGlycine
30g/QSodium G
lucon nate (sodium gluconate) 30g
/Q additive polyoxyethylene alkyl 5mg
/l During plating with sodium phenyl ether sulfate, the substrate is rotated around its axis in one plating tank, and the plating solution is stirred by the circulating flow of the plating solution. As plating progresses, the nickel concentration in the plating solution decreases, and p
H increases, and the amount and rate of change are measured using 10 absorbance meters and pH meters, and all zero analysis and replenishment operations for replenishing the corresponding amount are controlled by 12 control units. The replenishment liquid is divided into three systems, each consisting of a nickel sulfate solution, a hypophosphorous acid solution, and a caustic soda solution.

The 11 replenishment section consists of the above three types of tanks and a fixed replenishment pump. These three components are added to the circulating plating solution flow in the second supply section. The important point is to place the supply part 2 close to the suction port of the pump 3. The supplied replenishment solution is stirred and mixed with the plating solution by the pump, that is, by a large amount of the plating solution, which helps stabilize the plating solution.

Thereafter, the plating solution is pressurized by pump 3 and sequentially passes through 5 μm, 1 μm, and 0.2 μm filter system 4 to trap dirt and particles in the plating solution and clean it. A particularly high degree of defect-free property is required for the N1-P plating film used for underplating of substrates for magnetic disks. In order to achieve the signal error specifications for magnetic disks, the substrate must not have even one plating defect with a diameter of 5 μm or more. For this reason, ultra-precise filtration as described above is necessary.

The filtered plating solution is then heated in the heat exchanger 5,
The temperature of the liquid in the plating tank is adjusted to be maintained at 90" ± 0.5. This is done by installing a temperature detection sensor in the plating tank 1, and using a temperature controller to control the temperature of the heating section 5. This can be achieved by controlling the amount of 120°C steam.

Finally, the heated plating solution returns to the plating tank 1.
Plating continues.

After 2 hours, when the plating thickness is 15 μm, it is pulled out of the plating bath, followed by water washing, hot water washing, and drying steps to complete the N1-P plating film step for the magnetic disk.

As a result of evaluating the obtained 300 N1-P plated substrates, the film thickness distribution was 15 ± 0.8 μm, and the phosphorus content in the film was 12.
．． 5±0.2 wt%, and the magnetization strength after heating at 280° C. for 3 hours was 0.8 to 3.5 G, indicating excellent heat-resistant nonmagnetic properties.

When we measured the defects after plating, we found that 7 out of 300 substrates had plating defects larger than φ5μ, and the defect incidence rate was 2.
．． It was 3%. This means that when using the plating solution shown in the example and using a conventionally known plating device, the defective rate is approximately 7 to 7.
When compared with 10%, it was reduced to 1/3 or less.

Thereafter, the surface of the N1-P plated substrate was polished by mechanical processing to a surface roughness of about 0.008 μra Ra.

After washing and cleaning the polished surface, the substrate was placed in a sputtering device, and a Co-Ni-Cr magnetic film was formed using a 400-person sputtering method to form a recording film, followed by a 450-person sputtering process to form a protective film of carbon. The magnetic disk was completed by forming the magnetic disk using the method.

When we measured the electrical signal characteristics of the sputtered magnetic disk completed through the above process, we achieved a recording density of 31,000 OOB PI (bits/1 nch), and the signal Z error was OK/side yield was 46 disks. It achieved a high performance of 150 disks and completed a high-performance magnetic disk.

The magnetic disk formed in this example has a cross-sectional configuration of AQ.
/Ni-P/Co-Ni-Cr/C, but it goes without saying that the materials and configurations of the magnetic film and protective film are not limited to these.

In this example, the plating tank, piping, pump, and filter are used.
Qi Upper Section 1 - Although it was formed using a so-called fluororesin such as Kasuri-setsu or PVDF, it is of course possible to form a part of it from polypropylene.

Embodiment 5 The configuration of this embodiment is shown in FIG. The difference from the previous embodiment is that in FIG. 6, a cooling section shown at 6 and a supply system pump shown at 7 are provided.

In other words, in Example 4, the replenishment liquid was directly input into the circulating main flow of plating in the second replenishment section, whereas in this example, the replenishment liquid was input into the plating liquid that was separately drawn in and cooled.
These are combined upstream of pump No. 3. This will hereinafter be referred to as the plating solution for the supply system.

The purpose of providing a replenishment system is to replenish plating components without making the plating solution unstable.

The plating rate decreases rapidly as the liquid temperature decreases, and the plating reaction almost stops below 75°C.

If the replenishment solution is directly dropped into a high temperature state of 90° C., the plating solution becomes unstable, increasing the risk of solution decomposition, or forming fine particles in the solution, causing plating defects. Therefore, the plating solution should be cooled and replenished at about 60 to 80°C, more preferably at 65 to 75°C.

If the temperature is 80℃ or higher, cooling replenishment will not be effective.
If the temperature is below ℃, the amount of heat consumed by the entire plating equipment increases unnecessarily, and there is no benefit.

The liquid temperature during replenishment in this example was 75°C.

The main point of the replenishment system configuration is to cool the liquid before the pump, as shown in Figure 6, and then replenish the cooled liquid just before it enters the pump.This allows the pump to mix the replenishment liquid and plating solution. It can also serve as a mixer.

Incidentally, assuming that the flow rate passing through 4 and 5 is 100, the flow rate flowing into the replenishment system is preferably about 5 to 20.

If it is less than 5, the flow rate of the replenishment liquid flowing through 7 is too small, resulting in lack of stability in replenishment. If it is 20 or more, 5
The amount of heat required by the heat exchanger increases, the amount of heat consumed by the entire plating equipment increases, and no further effect is produced.

In this example, the ratio was set to 10.

Note that it is of course possible to install a filter to filter the plating solution after passing through the pump in step 7 before it joins the plating solution flow in the circulation system.

One of the effects and features of the apparatus configuration shown in FIG. 6 is prevention of plating precipitation inside the filter (4). This is because the liquid that was cooled to below 80°C in step 6 joins just before the pump in step 3, so the liquid that was at 90°C when leaving the plating tank in step 1 is also
Liquid temperature decreases. The degree of liquid temperature drop depends on the pump flow rate ratio between 3 and 7 and the temperature of the liquid passing through 7, but in this example it is 85.
It became ℃.

Since the driving force for the plating reaction and precipitation decreases considerably due to this drop in liquid temperature, the risk of N1-P precipitation accidents inside the pump 3 and the filter 4 can be greatly reduced. In conventional equipment, the liquid temperature is often filtered at 90°C, and as a result, the N1-P film sometimes precipitates from foreign matter captured inside the filter, and in extreme cases, the plating equipment has to be stopped.

One of the differences when comparing FIG. 6 and FIG. 5 is the difference in time from replenishment to heating.

As is clear from the figure, the time in the case of FIG. 6 is longer due to the passage through the flow path of the supply system.

After replenishment, a neutralization reaction and a chelation reaction between nickel and the complexing agent occur, but these reactions must be completed before the nickel comes into contact with the dangerously high temperatures of the heating section.

The case shown in FIG. 6 is preferable from the above point because the time from replenishment to overheating is longer due to the longer path through which the liquid passes. Specifically, it is effective in improving stability by preventing decomposition of the plating solution, reducing defects, and extending the life of the plating solution. It is important to determine the length of the piping route by considering the reaction time.

Thereafter, chemical N1-P plating was performed in the same manner as in Example 4 using 300 disk substrates made of 5086A Q alloy. As a result of pre-treatment, N1-P plating conditions, plating solution and measurement after N1-P plating, the film thickness distribution was 15±0.9
p va, the phosphorus content in the film was 12.6±0.2 wt%, and the amount of magnetization after heating at 280°C for 3 hours was 0.8 to 4.
Almost the same results as 0G and Example 1 were obtained.

The φ5μI5±1 defect occurrence rate on the plated surface was 2 of Example 4.
．． It decreased further from 3% to 1.0%.

Regarding the life of the plating solution, if one turn is defined as plating until all the nickel contained in the bath is replaced when the plating solution is prepared, in Example 4, plating defects increased after 4.2 turns were used. It was determined that the fluid lifespan was reached, and the fluid was renewed.

The apparatus of Example 5 was capable of plating up to 5.5 turns.

The reason why plating defects and solution life could be improved is that in Example 5, plating solution components could be replenished more safely and stably.

The substrate after N1-P chemical plating was machined in the same manner as in Example 4, and a magnetic recording layer and a protective film were formed thereon to complete a thin film sputtered magnetic disk.

When we measured the electromagnetic characteristics of this disk, it was 31,000B.
Achieved high recording density of PI, and also showed a high yield of 50 sides and 150 sides with no signal bit errors.
We were able to complete a magnetic disk with extremely excellent characteristics.

According to the fourth and fifth embodiments described above, since the replenishment liquid is introduced near the suction port of the pump, the pump itself can be used as an excellent stirring mixer.

Furthermore, by installing a heating section and a heat exchange section in the filter and plating calibration, the flow of the plating solution in the plating tank becomes simple and uniform, which improves the plating thickness distribution and makes it possible to use m≠ chemical resins or polypropylene materials. This has the effect of eliminating contamination from the plating solution tank and piping materials because essentially no plating reaction occurs on the surfaces of these materials.

〔Effect of the invention〕

N1 that can be formed by the plating method and plating solution of the present invention
- P-plated film has a stable amorphous structure, so it has excellent non-magnetic properties during high-temperature processing and low internal stress that causes substrate deformation, and has few plating defects, so it is especially suitable for sputtering. As a high-performance chemical nickel plating film for magnetic disk underlayers, it has superior properties compared to conventional technology.

Since the plating solution itself is stable, control solution management is easy and the plating solution has a sufficiently long life. Therefore, it has great features in terms of workability and economy.

Therefore, by using the present invention, it is possible to realize a high recording density sputtered magnetic disk, but
It is also possible to apply and put it to practical use in other types of electronic parts and heat-resistant functional parts that require N1-P plating films, and its industrial effects will be tremendous.

[Brief explanation of the drawing]

FIG. 1 is a characteristic curve diagram showing the results of EXAFS structural analysis of the N1-P plating film of the present invention, and FIG. 2 is a curve diagram showing the relationship between nickel-free ion concentration, pH, and complexing agent.
Figures 3(a), (b), and (c) are characteristic curve diagrams showing the relationship between the complexing agent/nickel molar ratio and the nickel-free ion concentration, and Figures 4(a), (b) , (c), (d
) are characteristic curve diagrams showing the relationship between the composition range of the complexing agent and the plating solution stability: number of turns, respectively, which are examples of the present invention. FIG. 5 shows an embodiment of the chemical nickel plating apparatus configuration of the present invention. FIG. 6 shows another embodiment of a chemical nickel plating apparatus in which the apparatus of FIG. 5 is provided with an improved supply system.謬 I month (P″1e-A; py* ) x ノρρEXAF-5t
SJss/-p Takipus no-m Shima Senne 1zu exposed = Isara n Yumi, 5□puss shoulder 2 group 4 torture<cL) j Ketsuto Ashishi two to thick 3. (”/ln 5th flash 6Z

Claims (1)

[Claims] 1. Hypophosphorous acid or its salt is dissolved as a reducing agent in a nickel salt aqueous solution, and equilibrium theory is applied in the entire pH range between the pH during plating and the pH of the alkaline replenishment solution. A chemical nickel plating solution characterized in that a combination of complexing agents is added in a selected manner so as to prevent precipitation of nickel phosphite and nickel hydroxide. 2. A chemical nickel plating solution characterized by dissolving hypophosphorous acid or its salt as a reducing agent and malic acid, glycine, and gluconic acid as complexing agents in a nickel salt aqueous solution. 3. The concentration of nickel constituting the chemical nickel plating solution is 0.09 to 0.20 mol/l, the concentration of hypophosphorous acid is 0.10 to 0.45 mol/l, and the concentration of malic acid is 0.1.
8-0.75 mol/l, glycine concentration 0.14-0
．． 50 mol/l, gluconic acid concentration 0.09-0.3
The chemical nickel plating solution according to claim 2, characterized in that it has a concentration of 0 mol/l. 4. A chemical nickel plating solution characterized by dissolving hypophosphorous acid or its salt as a reducing agent and malic acid, glycine, and ammonium as complexing agents in a nickel salt aqueous solution. 5. The concentration of nickel constituting the chemical nickel plating solution is 0.09 to 0.20 mol/l, the concentration of hypophosphorous acid is 0.10 to 0.45 mol/l, and the concentration of malic acid is 0.1.
8-0.75 mol/l, glycine concentration 0.14-0
．． 50 mol/l, ammonium concentration 0.09-0.
The chemical nickel plating solution according to claim 4, characterized in that the concentration is 30 mol/l. 6. The chemical nickel plating solution according to claim 2, 3, 4 or 5, characterized in that an anionic surfactant is added to the chemical nickel plating solution. 7. The anionic surfactant is selected from the group consisting of polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene alkyl ether phosphate, alkyl phosphate, and alkyl sulfate. 2. The chemical nickel plating solution according to claim 1, wherein the chemical nickel plating solution is at least one selected from the group consisting of fluoroalkyl carboxylic acid, fluoroalkyl sulfuric acid, fluoroalkyl phosphoric acid, and salts thereof. 8. The concentration of the anionic surfactant is 1 mg/l to 20
Claim 1 or 2 characterized in that the concentration is 0 mg/l.
Chemical nickel plating solution as described. 9. The concentration of the anionic surfactant is 5 mg/l to 10
Claim 1 or 2 characterized in that the concentration is 0 mg/l.
Chemical nickel plating solution as described. 10. The pH of the chemical nickel plating solution is 4.0 to 7.
10. The chemical nickel plating solution according to claim 1, wherein the chemical nickel plating solution is 0. 11. Step of preparing a desired substrate to be plated; Step of activating the surface of the substrate to be plated; Adding the activated substrate to a nickel salt aqueous solution with hypophosphorous acid or its salt as a reducing agent. and performing chemical nickel plating on the substrate to be plated by immersing it in a chemical nickel plating solution prepared by dissolving hydroxy acid, glycine, and either gluconic acid or ammonium as a complexing agent for nickel ions; and A method for using a chemical nickel plating solution, comprising the steps of lifting the substrate from the chemical nickel plating solution, cleaning it, and drying it. 12. Claim 11, wherein the hydroxy acid of the complexing agent is a chain hydroxy acid, specifically one selected from malic acid, citric acid, glycolic acid, and tartaric acid. How to use the chemical nickel plating solution described. 13. The method of using a chemical nickel plating solution according to claim 11 or 12, wherein the substrate to be plated is a nonmagnetic substrate. 14. The method of using a chemical nickel plating solution according to claim 1, 2 or 3, characterized in that the activation treatment comprises forming a metal film having a higher ionization tendency than nickel on the substrate to be plated. 15. The method of using a chemical nickel plating solution according to claim 11, 12, 13 or 14, characterized in that an anionic surfactant is added to the nickel plating solution. 16. Claim 13, wherein the nonmagnetic substrate is made of one of aluminum alloy, magnesium alloy, ceramics, glass, and plastics.
How to use the chemical nickel plating solution described. 17. Claim 14, characterized in that a zinc coating is formed as the metal coating that has a greater ionization tendency than the nickel.
How to use the chemical nickel plating solution described. 18. Prepare an aluminum alloy as the substrate to be plated, form a zinc film as an activation treatment process for the substrate, and add hypophosphorous acid or its salt as a reducing agent to a nickel salt aqueous solution as a chemical nickel plating solution. 12. The method of using a chemical nickel plating solution according to claim 11, further comprising dissolving malic acid, glycine and gluconic acid as complexing agents, and adding an anionic surfactant as an additive. 19. Prepare an aluminum alloy as the substrate to be plated, form a zinc film as an activation treatment process of the substrate, and add hypophosphorous acid or its salt as a reducing agent to a nickel salt aqueous solution as a chemical nickel plating solution. 13. The method for using a chemical nickel plating solution according to claim 12, further comprising dissolving malic acid, glycine, and ammonium as complexing agents, and adding an anionic surfactant as an additive. 20. The pH of the chemical nickel plating solution is 4.0 to 7.
20. The method for using a chemical nickel plating solution according to claim 11, 12, 18 or 19, characterized in that the chemical nickel plating solution is set to 0. 21. It consists of a plating tank, a circulation pump, a filter, a heating section, and a plating tank, and a circulation path for the plating solution is provided in this order, and between the plating tank and the circulation pump, the plating solution is 12. The method of using a chemical nickel plating solution according to claim 11, wherein the chemical nickel plating is carried out by replenishing consumed components of the plating solution. 22. The material of the plating tank, the circulation pump, the filter, the heating section, or the part of the piping that comes into contact with the plating solution is either fluororesin or polypropylene resin, or a combination of both. 22. The method of using the chemical nickel plating solution according to claim 21.